In the past, porous hair curlers have been developed that use steam to aid in curling--see for example, U.S. Pat. Nos. 3,759,271 (Caruso) and 4,453,554 (Caruso), both of which are hereby incorporated by reference in their entirety. Typically, as shown in FIG. 1, such hair curlers have a central portion 9 that includes a perforated cylindrical central core 12 that forms a passage 62 into which steam is directed from a steam source--for example, a table top steamer. The core 12 has rims 14 and 20 formed on each of its ends and is enclosed by a tubular porous sleeve 26 around which the hair 52 is wound, as shown in FIG. 2. The perforations 22 in the core 12 and the porous nature of the sleeve 26 allow the steam directed into the passage 62 to flow outward so that it is distributed to the hair 52 wound around the sleeve, thereby promoting the desired curling.
Generally, a semi-circular shield (not shown in FIGS. 1 and 2) is employed to at least partially enclose the sleeve 26 after the hair 52 has been wound there-around so that heat emitted by the steam is retained during the curling process. Various methods are known to secure the shield to the central portion 9. One such method, which relies on frictional resistance, is disclosed in the aforementioned U.S. Pat. No. 4,453,554. As disclosed therein, the shield has end walls formed on each of its ends. A slot in each of the end walls allows the end walls to be slipped over the core so that the shield is disposed between the rims and secured thereto by a friction or interference fit. The friction fit is obtained by carefully controlling the size of the components so that the length of the shield is slightly greater than the distance between the inside surfaces of the rims. This causes the end walls of the shield to bear against the inside surfaces of the rims. As a result of the contact between the shield end walls and the rims, motion of the shield relative to the core is restrained by friction, thereby preventing the shield from slipping off of the core. In addition, the width of the slot in the end walls through which the core is disposed corresponds generally to the diameter of the core, thereby providing additional frictional resistance to relative motion of the shield.
Unfortunately, the frictional resistance method of securing the shield to the curler has several serious drawbacks. First, obtaining the appropriate amount of interference between the shield and core is difficult. If the shield is too long relative to the core or the slots in the shield end walls are too narrow relative to the outside diameter of the core, there will be excessive interference, making it difficult to place the shield on the core. Alternatively, if the shield is too short relative to the core or the slots are too wide relative to the outside diameter of the core, there will be insufficient frictional resistance and the shield will not be adequately secured to the core. Consequently, obtaining the appropriate friction fit requires that the tolerance on the dimensions of the shield and core be tightly controlled, thereby increasing manufacturing costs and scrappage.
A second drawback of the frictional resistance method of securing the shield to the core is that it can cause problems in the curling process if the shield is improperly placed on the core. Such improper placement occurs if the shield is placed on the core so that one of its longitudinal edges presses down against the hair, especially in the bang area or when styling a page boy. Although the hair imposes a reacting force on the shield, the frictional resistance prevents the shield from rotating away from the hair so as to alleviate the pressure against the hair. Consequently, there is contact under pressure between the edge of the shield and the hair throughout the curling process. As a result, improper placement of the shield on the curler can cause an undesirable kink to be formed in the hair. Although users may be cautioned against such improper placement of the shield, such instructions are not always followed.
A third drawback of the frictional resistance method of securing the shield to the core is that lubricants used to facilitate the molding of the curler components can reduce the coefficient of friction so that the interference fit alone does not provide sufficient frictional resistance to adequately secure the shield on the core.
Another method for securing the shield to the central portion 9, which does not rely on a friction fit between the shield and the core, is disclosed in the aforementioned U.S. Pat. No. 3,759,271. According to this approach, after the shield is slipped over the core, one leg of a two legged hair clip, such as a bobby pin, is disposed through an arcuate hole in one of the rims so that the clip slips onto the end of the shield with the legs of the clip clamped around the shield, thereby fastening the shield to the rim. Like the friction fit method, this approach does not allow the shield to rotate freely with respect to the core, since the shield and rim are fastened together by the clip. As a result, kinking of the hair can occur if the shield is improperly placed on the core, as previously discussed. In addition, the use of a separate clip complicates the curling process.
Consequently, it would be desirable to provide a hair curler shield that was secured to the curler core so as to be substantially free to rotate without frictional resistance from the curler core or rims and in which the method for securing the shield to the core did not require close control of the dimensions of these components.
It would also be desirable to provide a hair curler shield that incorportated integral means for positively locking the shield onto the curler core.